# Optimizing the Strength and Toughness of V/Mo-Modified 0.22C–5.24Mn Steel by Short-Time Partial Austenitization Process

## TL;DR

A new steel treatment process improves strength and toughness by creating a layered microstructure with controlled precipitates.

## Contribution

A short-time partial austenitization process is introduced to optimize the mechanical properties of V/Mo-modified steel.

## Key findings

- The SPA process produced a multiphase microstructure with high yield strength and good low-temperature toughness.
- (V, Mo)C precipitates contributed about 108 MPa to the steel's strength.
- The steel achieved 1097 MPa yield strength, 14% elongation, and 33.3 J impact energy at −20 °C.

## Abstract

In order to obtain the good match between yield strength and low-temperature toughness, the short-time partial austenitization (SPA) process was employed for V/Mo-bearing 0.22C–5.24Mn steel. The initial microstructure after intercritical tempering was dual-phase ferrite and reversed austenite (RA), while the final microstructure consisted of ferrite, RA, and secondary martensite (SM) after being subjected to the SPA process. (V, Mo)C with disclike morphology mainly precipitated during intercritical tempering, and the aspect ratio of particles decreased, leading to the appearance of near-spherical morphology. After being subjected to SPA process, the resultant multiphase hierarchical microstructure (three layers: outer layer of ferrite, interlayer of SM, and inner layer of RA) enabled a high yield strength of 1097 MPa, a total elongation of 14%, and an impressive impact energy of 33.3 J at −20 °C. The strengthening contribution of (V, Mo)C precipitation was estimated to be about 108 MPa.